CN1089370A - Form the method for figure - Google Patents

Abstract

Translated fromChinese

一种形成图形的方法改善了光刻胶图形的轮廓。本方法包括下列各步骤：在有台阶的衬底上形成光刻胶层、用第一掩模将光刻胶层作第一次曝光，用第二掩模将由于台阶使光刻胶层很厚的部位作第二次曝光，以及将曝过光的光刻胶层显影。尤其是，在台阶处的厚光刻胶要进行充足的曝光，从而避免形成桥接或残胶，而获得改善了轮廓的图形。

A patterning method improves the profile of a photoresist pattern. The method comprises the following steps: forming a photoresist layer on a stepped substrate, exposing the photoresist layer for the first time with a first mask, exposing the photoresist layer due to the step with a second mask The thicker areas are exposed a second time, and the exposed photoresist layer is developed. In particular, the thick photoresist at the steps needs to be exposed sufficiently to avoid bridging or residue formation and to obtain improved profile patterns.

Description

Form the method for figure

The present invention relates to form the method for figure, more particularly, relate to the method that forms figure with simple manufacturing process, and improved the figure that provides at the graph outline of high stepped portions.

Adapt with a series of high integration and high-performance semiconductor device, caused a kind of structure of complexity.Therefore, be sought after on Semiconductor substrate, forming the technology of Micropicture.Everybody knows that such semiconductor device graph is that method by photoetching forms.

The method that forms figure by photoetching process is as follows: at first at the upper surface of the substrate of figure to be formed, on insulation course, conductive layer or semiconductor wafer, form its solubleness with illumination, for example ultraviolet light or X ray and the photoresist layer that changes.With the mask that is carved with figure, optionally with the predetermined position exposure, light just shines on the glue-line selectively.Then, developing was subjected to the glue-line of illumination, remove have high-dissolvability (being the exposure position under the positive glue situation) the photoresist position and stay the photoresist position of low solubility, so just form a kind of litho pattern.Be etched away the position of the substrate of photoresist, just formed figure.After having finished substrate etching, remove left photoresist, just can obtain to be used for about connect up, electrode, or the like required figure.

Though, can form Micropicture with this high resolution lithography method, finer figure produces also needs to improve relevant technology.

Here it is, at resist exposure and the Micropicture that develops and to expose to the sun and to be obtained after the photoresist of light, form the live width of figure by the same ratio of the live width of photomask pattern.Yet,, just be difficult to the figure live width that keeps constant because of there being various operating process in the photoetching.The deviation of this live width is because the difference of the energy dose that the photoresist of different-thickness traps, and since at the step place because of diffraction and reflection cause that light scattering produces (referring to " Silicon Processing for the VSLI Era " by S.Wolf and R.N. Tauber, Vol.1, P439,1986).

Fig. 1 is the process flow diagram that forms technology according to the figure of conventional single-layer lithography glue method.With reference to Fig. 1, below such figure forming process will be described in more detail.

When substrate rotates with 100 to 1000rpm. speed, photochromics is coated in the upper surface of substrate.Then, if substrate for example 2000 arrives the 6000rpm. rotation with at a high speed, this photochromics can spread out rapidly under centrifugal action, and forms the uniform glue-line of thickness on entire substrate.

Fig. 3 A and 3B represent the single glue-line method according to routine respectively, when forming figure at the step place, and the variation of photoresist thickness, and the graphics shape of back that develop at the step place.Shown in Fig. 3 A and 3B, because of on substrate, forming figure, having under the situation of step, can change the thickness of glue-line partly.Here it is as shown in Figure 3A, and the step place onsubstrate 1 top has formed thicker glue-line 2.Particularly, because the development of the labyrinth of highly integrated device has more increased many steps.If the glue-line of formed stepped portions is much thicker than other positions when the photoresist coating because of such complex step, so, when forming the photoresist figure, will cause figure bridge joint or cull or the like part to increase.

Fig. 3 B represent with the glue-line exposure of as shown in Figure 3A formation with develop and the photoresist figure 3 that obtains.Referring to Fig. 3 B, the photoresist of this step bottom promptly, corresponds to the thick especially position of photoresist thickness, is not removed entirely.Therefore, can see that photoresist is stayed between thelitho pattern 3, and indicate with label 4.

Cause this undesirable phenomenon to be because following situation.For forming good photoresist figure, when exposing, the focal length of light should adapt with the center line of photoresist thickness.That is, because of being symmetrical with respect to focus in the face exposure district of photoresist and the exposure region of photoresist lower surface, when focus and photoresist mid-depth met, the photoresist surface was the same with the exposure region of bottom each other, therefore, has precipitous light distribution.Yet, forming photoresist layer having on the disk of step, the thickness of this layer is fixing with the difference of substrate zone, so the mid-depth line of whole glue-line is matched with the focus of light.Here it is, and for example, because at the step place that suitable thick photoresist is arranged, the focal line of light is positioned at the top of the thick center line of photoresist, so exposure range becomes and is wider than exposure range under the photoresist.The exposure energy dosage that this means the photoresist bottom is short of relatively, that is, and and under-exposure.Undesirable live width change, bridge joint, cull layer or the like take place in under-exposed meeting.Therefore, the profile of this photoresist figure degenerates, so that can not etched substrate.

For solving the problems referred to above of conventional individual layer glue (SLR) method, and developed the method for a kind of many glue-lines (MLR).

According to the MLR method, the process flow diagram that figure forms technology is shown among Fig. 2.Sandwich construction when Fig. 4 represents by MLR method formation figure.With reference to Fig. 2 and 4, below the method for MLR will be described in more detail.

At first,, cure then than the thick a lot of following photoresist 11 that is used for complanation of substrate level in the coating of the top of substrate 1.After the top of photoresist 11 applied intermediate insulating layer 12 down, coating was in order to the last photoresist 13 of exposure, so form the multilayer glue-line.Exposure with develop on after the photoresist, again with this intermediate insulating layer of dry etching.After this, with oxygen (O₂) dry plasma etch lower plane photoresist, to form the photoresist figure.Then, utilize this photoresist figure to come etched substrate, remove the photoresist that stays again, just obtain figure.The MLR method can produce high resolving power, is less than or equal to the figure of 0.5 μ m.

The special permission that discloses in Japan discloses a kind of application that has disclosed the MLR method among the clear 51-107775.In the above-mentioned day disclosure, exist at substrate to slather on the substrate top of out-of-flatness position or step and apply one deck organic matter layer (lower floor), make the upper planeization of substrate, then, form by spin-coating glass (SOG), phosphorosilicate glass (PSG) or SiO at the top of substrate₂The middle layer of forming.So, according to conventional photoetching process, exposure with develop this top layer, etching middle layer again, thus predetermined shape is made in the middle layer.Make mask with the middle layer again, dry etching is removed the extending part of thick lower floor.After this, by being carved into the lower floor of figure, the extending part of the layer that dry etching will be made, thereby the predetermined figure of formation.

Also have, Korean Patent Publication No. 89-3903 has disclosed a kind of method that is used for improving MLR method graphics resolution.For accomplishing this point, by reducing the middle layer refractive index of light and upper strata and lower floor are made upper strata and middle layer to the difference between the refractive index of light, and each interface between middle layer and the lower floor all reduces the light reflection.Simultaneously, prevented because the interference of light in layer that difference produced of lower floor's layer thickness can be contained the change of size when figure forms.Method described in above-mentioned Korean Patent is open comprises that continuous deposit treats each operation of making layer, lower floor is made up of the organic polymer compound, the middle layer is by the made of the performance with anti-dry etching bigger than the lower floor on substrate and photosensitive upper strata, by selectivity to the exposure of the predetermined position on upper strata with developed in the position of the light that exposed to the sun, be formed with the last layer pattern of reservation shape, remove the lower floor position of exposing, and pass through and remove the extending part of substrate and form the substrate figure, wherein the difference of the optical index of the optical index in middle layer and upper strata or lower floor all is less than or equal to 12%.

Can obtain high-resolution Micropicture with the MLR method.But, because complex process, again by many operations, so throughput rate is low, the quantity of substandard product increases and the complete cost of manufacturing semiconductor technology has increased.

Therefore, the purpose of this invention is to provide a kind of energy acquisition has the pattern forming method of the figure of fine resolution, wherein owing to adopted the method for single-layer lithography glue, needn't be through the technology of complexity as the multilevel resist method, thus simplified technology, saved expense and made photoresist developing easily at the stepped portions thickening.

In order to finish above-mentioned purpose of the present invention, a kind of method that is used for forming figure is provided, comprise the following steps:

On substrate, form the step of photoresist layer;

At first, expose to photoresist layer with the 1st mask;

Secondly, give the quite thick position exposure of said photoresist layer with the 2nd mask owing to step; And

The photoresist layer of the light that exposed to the sun is developed.

With reference to accompanying drawing, by the detailed description to preferred embodiment of the present invention, above-mentioned purpose of the present invention and other advantages will become more obvious.

Fig. 1 is the process flow diagram that forms technology according to the figure of conventional single-layer lithography glue (SLR) method;

Fig. 2 is the process flow diagram that forms technology according to the figure of conventional multilevel resist (MLR) method;

When Fig. 3 A and 3B express respectively and form according to conventional single-layer lithography glue method figure, in the variation of step place photoresist thickness, and the graphics shape of back at the step place that develop;

Fig. 4 is when forming figure according to conventional MLR method, the sectional view of interlayer;

Fig. 5 is the process flow diagram according to formation graphics art of the present invention;

Fig. 6 A is the photoresist layer sectional view that a step is arranged;

Fig. 6 B and 6C are illustrated in the upper part of Fig. 6 A photoresist layer, and being used for the present invention is the arrangement Butut of the designed strip grate figure of the 2nd mask;

Fig. 6 D is illustrated in the photoresist layer upper part of Fig. 6 A, and being used for the present invention is the arrangement Butut of the designed a kind of grid figure of the 2nd mask;

Fig. 7 A to 7C represents to form according to the technological process of figure forming method of the present invention the process of figure;

When Fig. 8 A and 8B express respectively and form figure according to the SLR method of routine at the section of step place photoresist and the graphics shape at development backward step place.

By the preferred embodiments of the present invention,, then, expose once more by the thicker position of photoresist with the 2nd mask with resist exposure.Especially be necessary, in exposure machine, allow this photoresist layer expose continuously with the 1st mask and the 2nd mask.That is, need to make the 2nd mask graph, so that the size of 0.5 μ m to 400 μ m is arranged along stepped portions.Preferably, the 2nd mask graph of the manufacturing size that can align the 2nd mask graph by the thickness and the step degree of depth of photoresist.

Fig. 5 is the process flow diagram according to formation graphics art of the present invention.For form the present invention have step device have a high-resolution figure, with the mask that predetermined pattern is arranged, single-layer lithography glue is carried out first time exposes.Then, remove the thick photoresist of stepped portions effectively, carry out the 2nd exposure with the mask that predetermined pattern is arranged again.Just, after solving exposure for the first time, because it is low at thick photoresist position exposure energy dosage, cause the decomposition intensity of photoactivation compound (PAC) little, and make the thick photoresist position clean problem of developing, expose to stepped portions again, thereby replenish exposure energy dosage to increase the decomposition intensity of PAC.

The exposure energy dosage of the 2nd time required exposure is 5% to 20% of the 1st exposure dose.If energy dose is lower than 5%, then a little less than the exposure effect excessively, and if energy dose more than 20%, the resolution of figure increases and then increases with energy and reduce a little.If make the 2nd exposure energy dosage be weaker than exposure energy dosage the 1st time, even the position of the light that do not expose to the sun when inserting the 1st mask makes this position exposure when inserting the 2nd mask, that position can not become figure yet and stay, and does not develop again because exposure light amount is little.Owing to allow stepped portions double exposure, resist exposure is very abundant, so, even also can form clean figure in the edge of the light that exposed to the sun.

Especially, because the 2nd mask has the figure that matches with the thickening bondline top of step, so the 2nd mask does not almost resemble the Micropicture the 1st mask.Because the 2nd mask size is quite big, just make the 2nd exposure need be as the 1st the accurate mount mask of exposure.That is, do not have the rotation of mask, mutually vertical, or the like problem.Like this, according to method of the present invention, it is complementary increasing the 2nd exposure.Yet, can understand that when comparing with rotine exposure technology, though the 2nd exposure technology is quite simple, its effect is good.

In order to form better figure, when carrying out the 2nd exposure, preferably give defocusing of big approximate number micron with the 2nd mask.Like this defocus the graphics resolution that has improved the photoresist edge, wherein the 1st mask and the 2nd mask overlaid.Preferably, values of defocus is 0.5 to 20 μ m.

Also have, in the method according to formation figure of the present invention, in predetermined the 2nd figure of the 2nd mask, add complementary gate figure (X-or Y-direction) or grid figure, so that implement the 2nd exposure.

Fig. 6 A represents shaping gate figure (label 9 of Fig. 6 B and 6C) or grid figure (label 10 of Fig. 6 D) to 6D, is being provided with on the 2nd mask on the top ofphotoresist layer 2 that these figures will be configured in step (Fig. 6 A).

In this figure, the distance ' ' d ' ' between the bar grid (these grid are parallel with step to be inserted into) can be done suitably to adjust and configuration by the photoresist thickness that changes because of step.So, can make the variation of the dimension of picture degree that minimizes by the change of photoresist thickness.Assign into bar gate figure or the size of grid figure or the critical resolution that distance will be equal to or less than the peripheral region in the 2nd mask of predetermined pattern.Be exactly requirement, the 2nd figure that design is not because of defocusing shown figure.Best is that bar gate figure or grid figure can change its size or distance by the change of photoresist thickness.

Usually mask is divided into hard mask or soft mask.Yet, because of soft mask is difficult to form the Micropicture that is less than or equal to 2.5 μ m, so, rigid mask mainly adopted in field of semiconductor manufacture recently.Rigid mask applies the manufacturing of one deck shading layer material by means of sedimentation sputtering method or chemical vapor deposition method on substrate.Soda-lime, borosilicate or crystalline solid or the like can be used as the mask substrate material.Wherein, the price of crystalline solid is expensive especially.Yet the crystalline solid advantage is that thermal expansivity is minimum, and the transmitance of shallow ultraviolet light or deep UV (ultraviolet light) is all very high.Therefore, among the present invention, just need with the material of this crystal as mask substrate.

The oxide of silicon, iron oxide, chromium or chromium can be as the shading layer material that is coated on the mask.Particularly, to use the compound substance of chromium and chromium oxide in the present invention.

Except that the conventional mask that on substrate, applies chromium/chromium oxide, can also adopt reflection mask or phase shifting mask or the like as available in the present invention mask.

The present invention can be as the light of exposure, exposed to the sun with regard to photoresist and give poor solubility between the part of light and the non-exposed portion and can form figure, can be not restricted.As can be used for light of the present invention, can use KrF excimer laser (248nm) and ArF excimer laser (193nm) and g-line (436nm), i-line (365nm), h-line (405nm) and from the deep UV (ultraviolet light) (240-440nm) of mercury vapor lamp or Xe lamp.

Except that the reduced projection exposure method, projection exposure method, X-x ray exposure x method wait all to can be used as exposure method without any exception one to one.

Usually photochromics is divided into positive type or negativity type.Negativity type photochromics is made up of the potpourri of thermoprene base resin and bisdiazo based compound.The position of shining light forms reticulate texture by cross-linked material (two even based compound) and is hardened, and the non-exposed area is then gone with developer is molten.On the other hand, the positive type photochromics normally is made up of the phenol resin and the organic solvent of benzoquinones diazo photochromics, alkali soluble.By illumination, will be alkaline insoluble resin originally, be transformed into the resin of alkali soluble.Because positive light-sensitive material discrimination rate than negative material height, extensively adopts the positive type photochromics recently.

As the photochromics that the present invention can use, no matter positivity still is can both using of negativity.But, as mentioned above, require to use the positive type material that high-resolution is arranged.As the positive type photochromics that the present invention can use, can use phenolic group resin potpourri, chemical enhanced resin compound or chain rupture resin compound.

Hereinafter, will explain the preferred embodiments of the present invention.But, the invention is not restricted to this.

Embodiment 1

Comprise the photoresist of phenolic group resin and diazo naphthoquinone in the substrate top spin coating that step is arranged, forming thick is the photoresist layer of 1.2 μ m.With the ultraviolet light of g-line (436nm), adopting has the predetermined transistor mask of metallic pattern to aim at exposure.Subsequently, in fact remove thick photoresist,, insert the 2nd mask, have design size to be approximately the figure of 9 to 10 μ m in this mask in the direction identical with the metallic pattern direction in stepped portions.Then, with the 1st exposure energy about 10% can flow control continue to give the resist exposure that has exposed for the 1st time for 2 times.Here,, make the focus of the 2nd mask move on to about 5 μ m, expose with this in order to defocus.Subsequently, the alkaline aqueous solution with Tetramethylammonium hydroxide (TMAH) carries out wet development and forms the photoresist figure.The substrate that utilizes formed photoresist figure to come etching to make is removed the photoresist that stays again, thereby obtains required figure.

Embodiment 2

The same procedure of describing withembodiment 1 forms photoresist layer on the substrate top that step is arranged.With g-line ultraviolet light (436nm), employing has the predetermined transistor mask of metallic pattern to aim at exposure, subsequently, in fact remove the thick photoresist of stepped portions, in that direction identical with metallic pattern, insert the 2nd mask, and have design size to be about the figure of 9 to 10 μ m in this mask, and will wherein be of a size of bar gate figure or the checkerboard pattern alignment of 0.1 to 0.2 μ m.Then, (the 2nd time) continues to give the photoresist that has exposed for the 1st time to aim at exposure at the step place with about 10% energy of the 1st exposure energy.Here, in order to defocus, to make the 2nd mask move 5 μ m, and expose.Subsequently, the alkaline aqueous solution with Tetramethylammonium hydroxide (TMAH) carries out wet development and forms the photoresist figure.The substrate that utilizes formed photoresist figure to come etching to make is removed the photoresist that stays again, thereby obtains required figure.

In the above embodiments, can improve the smooth finish at pattern edge position, wherein superimposed by defocusing with the 1st mask and the 2nd mask, and can improve the effect of bar gate figure or checkerboard figure.

Fig. 7 A represents according to the technological process of the method for formation figure of the present invention to 7C and forms the process of figure.Fig. 8 A and 8B represent by the 1st embodiment and the resulting figure of the 2nd embodiment, the graphics shape at the step place.

To 7C and Fig. 8 A and 8B, below the above embodiments will be described in more detail with reference to Fig. 7 A.

To shown in the 7C, this photoresist is through the 1st exposure (Fig. 7 A) as Fig. 7 A.In the photoresist of the 1st light that exposed to the sun, thephotoresist 6 at the step top is not exposed, and thephotoresist 7 in the step bottom will stand the 2nd exposure (Fig. 7 B), and what obtain double exposing is photoresist 8.Then, by post exposure bake (PEB) and development, just form smooth photoresist figure 3(Fig. 7 C that stepped portions does not have bridge joint or cull).

Shown in Fig. 8 A and 8B, the photoresist figure (Fig. 8 B) that obtains is being represented corresponding to the photoresist (Fig. 8 A) in stepped portions, from Fig. 8 A of the present invention and 8B as can be seen, and in whole zone, comprise thestep bottom section 5 that is easy to occur defective, formed entire figure.

As mentioned above, if make Micropicture,, just can obtain the photoresist figure that good profile is arranged that could obtain by the MLR method as long as use single-layer lithography glue by the present invention.By using two masks, double expose, just can reach this purpose simply.

That is, according to the present invention, ratio of defects extremely low (except the defective of photoresist own), and also technology is simple, thus obtain the effect of boosting productivity with cost saving.Like this, even step is arranged, also can form Micropicture at an easy rate.

Though shown particularly and described the present invention with reference to preferred embodiment, but those skilled in the art understands, wherein can make the change on many forms or the details and can not depart from the spirit and scope of the present invention that limited by the appended claims.

Claims (11)

1, a kind of method that forms figure comprises the following steps:

Has formation one deck photoresist on the substrate of step;

Use first mask, give described photoresist layer exposure for the first time;

Use second mask, give for the second time owing to described step makes the quite thick position exposure of described lithography layer; And

The photoresist layer of light of will exposing to the sun develops.

2, according to the process of claim 1 wherein the size of adjusting described second mask graph according to the degree of depth of the thickness of photoresist layer and described step.

3, according to the process of claim 1 wherein in exposure machine with described first and second masks with the photoresist layer continuous exposure.

4, according to the process of claim 1 wherein the exposure energy of described second time of step of exposure be described first time step of exposure 5 to 20%.

5, according to the process of claim 1 wherein that the figure of described second mask has the size of 0.5 to 400 μ m along stepped portions.

6, defocus according to the process of claim 1 wherein when exposing the described second time, to give.

7, according to the method for claim 6, wherein defocusing is 0.5 to 20 μ m.

8, according to the process of claim 1 wherein that described second mask has a gate figure or a grid dish-type figure.

9, according to the method for claim 8, wherein said gate figure or described grid dish-type figure can change its size or distance according to the change of photoresist thickness.

10, according to the method for claim 8, the size of wherein said gate figure or described grid dish-type figure is not more than critical resolution.

11, according to the method for claim 8, wherein said gate figure or described grid dish-type figure by defocusing, remain and have the figure that is not more than critical resolution in described second time step of exposure.

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